TABLE OF CONTENTS MIMO is associated with exploiting the spatial domain of the propagation channel and involves sophisticated signal processing. The employment of antenna arrays at both sides of the link is essential for MIMO, hence antennas are an important aspect. Finding feasible antenna configurations is an integral part of enabling the MIMO technology. In this section, different antenna configurations for MIMO are investigated.
MIMO systems exploit the multipath structure of the propagation channel. The antennas are adapted to the propagation channel. Both the antenna arrays and the propagation channel should be treated together and described statistically to take many channel realisations of a propagation environment into account. Correlations among channel coefficients are influenced by the antenna properties. As the antennas are colocated in a MIMO array, mutual coupling effects may occur. All these effects should be considered when designing an antenna array for MIMO systems.
For the evaluation and comparison of different antenna concepts for MIMO systems quality measures are needed. In Subsection 6.4.1, an overview over these specific measures is presented. Different antenna configurations are compared. It becomes clear that power effects should be taken into account, hence power effects are discussed in Subsection 6.4.2. The effects of polarisation diversity and mutual coupling among the antenna elements are addressed. The integration of MIMO antenna arrays into small handsets is a major challenge, because usually a large antenna spacing is needed for the exploitation of the spatial properties of the propagation channel. In Subsection 6.4.3 several examples are given...
